绝缘罩不得磨损、划伤,安装位置不得颠倒,有引出线的要一律向下,需紧固的部位应牢固严密,两端口需绑扎的必须用绝缘自粘带绑扎()层以上。
A.一
B.二
C.三
D.四
参考答案:B
Mark ________ have hurried. After driving at top speed, he arrived half an hour early.[ ]
A. needn't
B. wouldn't
C. mustn't
D. couldn't
不属于社会问题特征的是( )
A.普遍性和变异性
B.复合性和周期性
C.破坏性和集群性
D.暂时性和间歇性